The invention relates generally to the preparation of materials to be used in particulate form, the term "preparation" as used herein being understood to emcompass "regeneration". Of particular interest to the invention is the treatment of used foundry sand.
The cleansing or treatment of the used sand generated in very large quantities in foundries after each molding or casting operation is a problem which has not yet been satisfactorily solved. This used sand is primarily present in bulky form, that is, in the form of lumps and the like which are sometimes of substantial dimensions. These lumps must be comminuted and the sand particles finally obtained then freed from the coating of binder which surrounds them. The binder in the used foundry sand constitutes a contaminant for the sand and as used herein, the term "contaminant" will be understood to include the binder present in the used foundry sand. Various apparatus such as ball mills, crushers, hammer mills and the like are used for the purpose of comminuting the hard lumps. The removal of the binder coating from the sand particles is performed subsequent to the comminution of the lumps using various methods such as mechanical, pneumatic, thermal or chemical processes.
The above manner of treating used foundry sand is a complicated one and, hence, is expensive. Moreover, the results obtained are often unsatisfactory, this being particularly true in those cases where the binder to be removed is one based on synthetic resins such as, for example, furan resins.